Control valve for hydraulic presses



Jan. 21, 1941. J. M. TOWLER ETAL 2 414,56

CONTROL VALVE FOR HYDRAULIC PRESSES Filed Feb. 18, 1943 2. Invenlons M i flu Attorney Patented Jan. .21, 1947 UNITED STATESkPATENT oFFicE CONTROL VALVE FDR HYDRAULIC PRESSES John Maurice Towler and Frank Hathorn Towler,

Yorkshire, England, assig'nors to Electraullc Presses Limited, R'odley, England Application February 18, 1943, SerialNo. 476,353 In Great Britain December 8, 1942 This invention relates to a valve for controlling the release of pressure liquid from an hydraulic press to exhaust of the kind comprising a main outlet which permits of a sudden release of pressure liquid from the press and a subsidiary outlet of restricted area which permits of a gradual release of pressure liquid from the press and valve means controlling the escape of liquid through said main outlet said valve means operating automatically to close the main outlet when a predetermined pressure of the liquid in the press is reached whereby the initial release of pressure liquid from the press occurs gradually through the restricted subsidiary outlet and to open the main outlet to permit of a sudden re lease of the pressure liquid from the press when the pressure of said liquid falls to a predetermined safe level.

The object of the present inventionsis to provide an improved control valve of the above type.

In the improved valve according to the present invention the valve plunger is moved in one direction by the fluid pressure in the press cylinder and in the opposite direction by a spring acting in opposition to the said fluid pressure and a variably restricted passage is provided between the valve plunger and the valve bore to permit the fluid in the press cylinder to escape to exhaust, means being provided to damp the movement of the valve plunger so that it moves slowly and, as the pressure falls in the press cylinder, the movement of the valve plunger in relation to the valve bore causes the said restricted passage to be gradually reduced in length and/or increased in area until the valve is ,fully open to exhaust, thereby ensuring that the pressure in the press cylinder is gradually released.

In a valve according to one embodiment of the present invention means is provided which functions as a non-return valve to permit both a free flow of liquid to the press cylinder and a restricted flow of liquid from the press cylinder to exhaust. This non-return valve in this embodiment is carried by the valve plunger but is capable of independent movement under the inlet pressure to open and pass liquid to the press cylinder. The restricted outward flow of liquid from the press cylinder to exhaust past the non-return valve is permitted by providing between the non-return valve and the bore for the valve plunger, a tapering passage the eflective area of which gradually increases as the valve plunger moves to the fully open position thus permitting a gradual release of pressure in the press cylinder. The minimum effective area of the tapering passage may con- 7 Claims. (Cl. 137-153) veniently be varied by providing an adjustable Instead tr the non-return valve being carried by the valve plunger it may be a separate valve arranged in or associated with the valve casing. If such a modified construction is adopted the loose bush in the first described arrangement will then form a rigid part of the valve plunger and be provided with a tapered flat to form the restricted orifice.

In order that the invention may be clearly understood and carried into eflect an example of the above preferred embodiment will now be described by aid of the accompanying drawing in which:

Fig. 1 is a sectional elevation taken longitudinally through .the valve and showing the valve plunger hard up against the. adjustable stop which limits its closing movement.

Fig. 2 is a similar view but showing the valve plunger in its fully open position.

Fig. 3 is a perspective view showing, isolated the non-return valve carried by the valve plunger.

In the valve illustrated the valve plunger (1 is of the packingless piston type and is provided with a portion b of reduced section which in the open position of the valve shown in Fig. 2 provides a free passage for pressure liquid, from a pump or accumulator, not shown,'entering the inlet c, to pass to the outlet d on its way to the press cylinder, and a further reduced portion e on which is slidably mounted a loose bush f adapted to function as a non-return valve. a still further reduced portion 9 is mounted a bush h which constitutes a damping piston to reduce the rate of the return movement of the valve plung r to the closed position shown in Fig.1.

The valve plunger, with the bushes f and h, slides within a parallel bore i in the casing 7, and opposite the outlet d is an enlarged circumfertial recess k, the interior of which is in permanent communication with the outer side of the I fixed bush or piston h and with a recess 1 by means of a shallow passage m. This passage is provided, for example, by forming a parallel flat surface along-the outer face of the fixed bush or piston. There is thus provided a passage of restricted area along which the pressure liquid in the recess k may flow to and escape from the outer'side of the fixed bush or piston h.

The loose bush or non-return valve 1 is urged to the right in the drawing by means of a light spring n the pressure of whlch'ls overcome by cargoes the bush and pass freely to the outlet d when the be held firmly in the closed position shown m Fig.

1 by the pressure of the liquid in the recess 1:,

' to prevent the free flow of liquid from the press cylinder to exhaust, but a-restricted fiow oi such liquid is permitted by providing the non-return valve with a restricted passage consisting, in the example illustrated, of a tapered flat formed across the outer circumference of the non-retum valve for a distance which permits the fiat slightly to overlap the recess I: when the valve plunger is in its closed position. In this position of the valve plunger the tapered fiat provides a passage of very restricted area through which the liquid from the press cylinder may pass irom'the recess is to the inlet 0 and so to exhaust.

The valve plunger is moved to the closed position by the pressure liquid in the recess k'acting against the exposed area of the valve plunger 1:, which pressure liquid is at substantially the same pressure as exists in the press cylinder. As the liquid in the press cylinder escapes to exhaust its pressure gradually falls, thus permitting the presure liquid on the outer side of the fixed bush to escape along the restricted passage m into the recess is. This gradual tau in pressureon the outer end of the valve plunger permits a spring 1) acting against the opposite end of the plunger to 2 move the plunger comparatively slowly to the open position illustrated in Fig. 2 and to carry with it the loose bush or non-retum valve 1 thus causing a gradual increase in the efiective area of the passage 0 and so permitting the liquid from the press cylinder to be gradually released to exhaust. This opening movement of the valve plunger is constrained to take place comparatively slowly as it is resisted by the pressure liquid which is trapped on the outer side of the fixed bush or damping piston h and thus can only escape slowly through the'restricted passage m.

The minimum effective area of the passage 0 through which liquid from the press cylinder may escape to exhaust whenthe valve plunger is in the closed position shown in Fig. 1 is rendered then have to take place through the restricted orifice provided by the tapering passage 0. As this exhausting proceeds the pressure behind the damping piston h will slowly tall and allow the D P radually to return the valve plunger to its open position. During this opening movement of the valve plunger the effective area of the orifice provided by the passage 0 will gradually increase thus gradually releasing the pressure to exhaust. This throttled exhaust will continue until the valve plunger is moved sufiiciently to the left to withdraw the non-return valve to its open position when exhaust will be free.

Although the valve of the present invention ha been described as for use-ln connection with hydraulic presses it may also be used for controlling the exhausting oi any hydraulic cylinder.

By the term "packingless piston type is meant a valve in which a close fit between the valve piston and its bore is relied upon for fluid-tightness. Such a valve may include an oil seal to collect leakage as in the, example illustrated.

What we claim is:

1. A hydraulic valvecomprising a housing having a bore, a first and a second port communicating with said bore, a plunger reciprocable in said bore between an open position and a closed position, spring means urging the plunger toward its open position, said plunger being automatically movable to its closed position in response to a predetermined increase in the pressure of the liquid, a non-return valve surrounding said plunger and slidable therealong to permit free flow of the pressure liquid from the first to the second port when the plunger moves to its closed position, said valve preventing free flow of liquid variable-by means of an adjustable screwed stop the valve plunger.

In use a control valve according to the present invention is interposed between a main con- ,trol valve, not shown, and the press cylinder, also until this pressure i sufilcient to overcome the spring 1 when the valve plunger will .be moved to the right until it abuts against the adjustable stop q. The delivery of pressure liquid to the press will, however, continue by the displacement of the non-return valve f until the main control .valve is operated to cut oil. the supply of pressure liquid and connect the press cylinder to .exhaust. When this is effected the non-retum ,valve will close and thus prevent a sudden discharge of liquid to exhaust. Instead, exhaust will It q which serves to limit the closing movement of housing having a bore, a-first and a second port communicating with said bore, a plunger reciprocable in said bore between an open position and a closed position, spring means urging the plungertoward its open position, said plunger being automatically movable to its closed position in response to a predetermined increase in the pressure of the liquid, a non-return valve mounted on said plunger and for sliding movement therealong between fixed extreme positions to permit free flow oi the pressure-liquid from the first to the second port when the plunger moves to its closed position and to prevent free flow from the second to the first port in the closed position of the plunger, and a passage oi. limited area formed on the periphery of said valve to permit reduced escape of the pressure liquid to the first port until the pressure of the liquid has fallen suiliciently to allow said spring means to return the plunger to its open position, said passagebeing so conformed as to provide a graduall increasing passage area for the liquid escaping to the first port response to a predetermined increase in the pressure of the liquid, at non-return valve surroundin said plunger and slidable therealong to permit free flow of the pressure liquid from the first to the second port when the plunger moves to its closed position and to prevent free fiow from the second to the first port in the closed position of the plunger, a tapered fiat formed on the periphery of said valve to provide a passage permitting reduced escape ofthe pressure liquid to the first port until the pressure of the liquid has fallen sufiiclently to allow said spring means to return the plunger to its open position, and stop means for limiting the closing movement of the valve plunger to vary the minimum effective area of the passage provided by said tapered flat.

4. A hydraulic valve comprising' a housing having a bore, a first and a second port communicating with said bore, a plunger reciprocable within said bore between an open position and a closed position, spring means for urging the plunger towards its open position, said plunger being automatically movable to its closed position in response to a. predetermined increase in the pressure of the liquid, a non-return valve mounted on said plunger and slidable therealong between fixed extreme positions to permit free flow of the pressure liquid from the first to the second port when the plunger moves to its closed position and to prevent free fiow from the second to the first port in the closed position of the plunger, and apassage of restricted area in said non-return valve for permitting reduced escape of the pressure liquid to the first port until the pressure of the liquid is reduced sumciently to allow said spring means to return the plunger to its open position.

5. A hydraulic valve comprising a housing having a bore, a first and a second port communicating with said b0re, a plunger reciprocable in said.

bore between an open position and a closed position, spring means urging the plunger toward its ing with said bore, a plunger reciprocable in said bore between an open position and a closed position, spring means urging the plunger toward its open position, said plunger being automatically movable to'its closed position in response to a predetermined increase in the pressure of the liquid, a non-return valve surrounding said plunger and slidable therealong within the bore to permit free flow of the pressure liquid from the first to the second port when the plunger moves to its closed position and to prevent free flow from the second to the first port in the closed position of the plunger, and a passage of restricted area formed at the periphery of said valve to permit reduced escape of the liquid to the first port until the pressure has fallen sufliciently to allow said spring means to return the plunger to its open position, said valve being movable conjointly with the plunger during the return stroke of the latter.

6. A hydraulic valve comprising a housing havopen position, said plunger being automatically movable to its closed position in response to a predetermined increase in the Pressure of the liquid, a bush surrounding said plunger and slidable therealong within the bore to permit free flow of the pressure liquid from the first to the second port when the plunger moves to its closed position and to prevent free flow from the second to the first port in the closed position of the plunger, a passage of restricted area between said vbush and the bore permitting escape of the liquid to the first port at a reduced rate until the pressure of the liquid has fallen suificiently to allow' said spring means to return the plunger to its open position, and means for damping the return movement 01' the plunger comprising a piston carried by the plunger having a, passage of restricted area through which liquid is passed to the outer side of the piston during the free flow of the liquid from the first to the second port and slowly discharged from said outer side of the piston during the return stroke of the plunger,

7. A hydraulic valve comprising a housing having a bore, a. first and a second port communicating with said bore, a plunger reciprocable in the bore between an open position and a closed position, spring means acting on one end of said plunger to urge the same towards its open position, said plunger being movable to its closed position in response to a predetermined increase in the pressure of the liquid, a piston on the other end of the plunger, a restricted passage in said piston permitting pressure liquid to pass to the outer side of the piston, the plunger comprising the plunger to prevent tree fiow from the second through said restricted passage in the piston following the gradual fall in the pressure 01' the liquid determined by the gradual release thereof to the first port. JOHN MAURICE TOWLER. FRANK HATHORN. "I'OWIER. 

